ML20034E684
| ML20034E684 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/25/1993 |
| From: | William Cahill, Woodlan D TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TXX-93108, NUDOCS 9303010192 | |
| Download: ML20034E684 (2) | |
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h6 Log
- TXX-93108 File # 10010 1-0 904.4 rr rr
,Ref. # 10CFR50.34(b)
TUELECTRIC February 25, 1993 William J. Cahill, Jr.
Gump Vwe hesident U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, DC 20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 MARGIN IN TU ELECTRIC DNB METHODOLOGY Gentlemen:
This letter is to document discussions between TU Electric (Whee Choe) and the NRC (Frank Orr) regarding TU Electric's planned method of treating DNB penalties.
TU Electric currently uses a deterministic DNB methodology in which the uncertainties in input parameters are assigned in a manner which yields the greatest challenge to DNB acceptance criteria.
Using this deterministic methodology, TU Electric proposes to maintain a DNBR safety analysis limit of 1.37.
This provides a margin of 0.21 to the TUE-1 correlation limit of 1.16.
This margin will be used to compensate for known and unknown DNB penalties (e.g., rod bow and mixed core).
In the near future, TU Electric intends to use the Statistical Combination of Uncertainties (SCU) methodology as described in TU Electric's Topical Report RXE-91-002.
Upon implementation of the SCU methodology, TU Electric will quantify the safety analysis limit to be used with the methodology.
This limit will be based on two factors.
The first factor (A) will be the DNBR uncertainty due to the combination of the input parameter uncertain'Aes.
The second factor (B) will be the margin to be retained tu account for known and unknown DNB penalties.
These factors will be determined at the time that the SCU methodology is completed to ensure that ample margin to cover known and unknown DNB penalties exists.
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TXX-93208 Paq*e 2 of 2 To summarize, the current TU Electric deterministic DNBR safety analysis limit for the TUE-1 correlation will be 1.37.
This provides a margin of 0.21 above the correlation limit which will be allocated by TU Electric to compensate for known and unknown DNB penalties.
Upon implementation of the SCU methodology, TU Electric will establish a DNBR safety analysis limit at a value of 1.16 + A + B, where A and B are as defined above.
Similarly, the margin above the correlation limit established for the SCU DNB methodology will be allocated by TU Electric to compensate for known and unknown DNB penalties.
Sincerely, William J.
Cahill, Jr.
By:
CT' D. R. Woodlan Docket Licensing Manager BSD/grp c - Mr. J. L. Milhoan, Region IV Resident Inspectors, CPSES (2)
Mr. T. A. Bergman, NRR Mr.
B. E. Holian, NRR
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